Vulnerability Discussion

A locally logged-on user who presses Ctrl-Alt-Delete, when at the console, can reboot the system. If accidentally pressed, as could happen in the case of a mixed OS environment, this can create the risk of short-term loss of availability of systems due to unintentional reboot. In the graphical environment, risk of unintentional reboot from the Ctrl-Alt-Delete sequence is reduced because the user will be prompted before any action is taken.

Check

Verify the Ubuntu operating system is not configured to reboot the system when Ctrl-Alt-Delete is pressed when using a graphical user interface.

Check that the "logout" target is not bound to an action with the following command:

# grep logout /etc/dconf/db/local.d/*

logout=''

If the "logout" key is bound to an action, is commented out, or is missing, this is a finding.

Fix

Configure the system to disable the Ctrl-Alt-Delete sequence when using a graphical user interface by creating or editing the /etc/dconf/db/local.d/00-disable-CAD file.

Add the setting to disable the Ctrl-Alt-Delete sequence for the graphical user interface:

[org/gnome/settings-daemon/plugins/media-keys]
logout=''

Update the dconf settings:

# dconf update